Depolarization in a photosensitive relaxor ferroelectric

This paper reports a study of depolarization of a photosensitive relaxor ferroelectric Sr0.61Ba0.39Nb2O6 with 0.44 at. % La and 0.023 at. % Ce impurities at room temperature and under illumination of up to 0.22 mW/cm2 in the absorption band of the crystal. The best fit to the experimental data was found with a function containing two time-dependent power-law terms. The approximation reflects two simultaneously operating polarization decay mechanisms, more specifically, polydomainization in the depolarizing field of a bounded crystal and screening of this field by photoinduced carriers. Exact double-humped distribution functions of nonexponential relaxation centers in the crystal have been derived from the relaxation times. Illumination shifts the distribution functions toward longer relaxation times.